Modify find_xcode.py to make --version optional
Modify find_xcode.py to make --version optional

Not specifying --version will just list what's currently installed.

BUG=480108
TESTED=scp'd to a bot, ran successfully with and without --version
R=dba@chromium.org

Review URL: https://codereview.chromium.org/1122603002

git-svn-id: 239fca9b83025a0b6f823aeeca02ba5be3d9fd76@295112 0039d316-1c4b-4281-b951-d872f2087c98

eunchong/build,eunchong/build,eunchong/build,eunchong/build